1. Technical Field
The present disclosure relates to Global Navigation Satellite Systems and, more particularly, to global navigation satellite antenna systems and methods.
2. Description of the Background Art
The present disclosure relates to Global Navigation Satellite System (GNSS) antenna systems and methods.
GNSS refers to various satellite based navigation systems used to determine the position of a user's receiver virtually anywhere in the world. Several GNSS systems are presently in operation including, for example, the Global Positioning System (GPS) operated by the United States of America and the Global Orbiting Navigation Satellite System (GLONASS) operated by the Russian Federation. GNSS is used extensively by both military and civilian sectors.
Each GNSS includes a plurality of satellites working together with a network of ground stations using a form of triangulation to locate the user's receiver. Each satellite transmits coded signals at precise intervals. The user's receiver converts the received signals into position, velocity and time estimates. The receiver can then calculate the exact position of the transmitting satellite and the distance (from the transmission time delay) between it and the receiver. By coordinating signal data from multiple satellites, the receiver is capable of determining its position.
Although GNSS provides a highly reliable and accurate ability to locate a receiver's position, it is not without fault. GNSS performance can be subject to several errors including ionosphere delay, troposphere delay, receiver noise and multipath. Multipath (also referred to herein as phase multipath and pseudorange multipath) is the major source of error in GNSS applications.
Multipath refers to a phenomenon occurring when a wave from a single source travels to a receiver via two or more paths resulting in components of the same wave being out of phase. This can occur, for example, because of extraneous reflections of the signal from objects such as buildings, the ground, trees, water surfaces, etc. Under the right conditions, the two (or more) components of the wave can interfere resulting in tracking errors in the receiver.
Various techniques have been used in attempts to mitigate problems caused by multiphase including improved antenna designs, improved receiver internal architecture and improved post-processing techniques.
In optimal conditions, GNSS systems allow for mm-level positioning. However, in environments suffering from multipath, the errors can grow by a factor of 2-5. Accordingly, phase multipath remains a major problem in GNSS positioning